Close-up control method and apparatus for variable focal length camera

Abstract

A variable focal length camera has a lens barrel movable parallel to the optical axis of its taking lens system so as to change over the focal length of the taking lens system at least between a standard photography position and a telephoto position. When the subject distance is nearer than the nearest focusable distance for standard photography or for telephotography, the lens barrel is automatically moved into a first close-up position if the lens barrel has been in the standard photography position, whereas the lens barrel is moved into a second close-up position if the lens barrel has been in the telephoto position.

What is claimed is: 
     
       1. A close-up photography control apparatus for a camera having a movable lens barrel for holding a taking lens system therein, and lens barrel driving means for moving said lens barrel in the direction of the optical axis of said taking lens system so as to change the focal length of said lens system, said control apparatus comprising: an encoder for outputting a plurality of signal patterns according to the position of said lens barrel, said signal patterns indicating a standard photography position, a telephoto position, a first close-up position for close-up photography into which said lens barrel can shift from said standard photography position, and a second close-up position for close-up photography into which said lens barrel can shift from said telephoto position, said encoder comprising a brush member movable in proportion to said lens barrel, and a contact pattern provided on a stationary printed circuit board and adapted to be swept by said brush member, said contact pattern including at least a column of contacts for defining a standard photography zone, a first close-up zone, a telephoto zone, and a second close-up zone covering respectively said standard photography position, said first close-up position, said telephoto position and said second close-up position;   a close-up determination means for determining whether the distance to a subject to be photographed is nearer than a minimum focusable distance predetermined for said telephoto position and a minimum focusable distance predetermined for said standard photography position; and   control means for controlling said lens barrel driving means, such that if said close-up determination means determines that said distance to said subject is nearer than said minimum focusable distances, said control means controls said lens barrel driving means to move said lens barrel into said first close-up position when said lens barrel is in said standard photography position, and into said second close-up position when said lens barrel is in said telephoto position.   
     
     
       2. A close-up photography control apparatus as defined in claim 1, wherein the position of the lens barrel is detected only upon the brush member leaving a contact of said contact pattern. 
     
     
       3. A close-up photography control apparatus as defined in claim 1, wherein said contact pattern comprises a second column of contacts parallel to said first column, said second column comprising contacts for defining respectively said standard photography position, said first close-up position, said telephoto position and said second close-up position. 
     
     
       4. A close-up photography control apparatus as defined in claim 3, wherein one end of each contact of said second column is shifted from one end of an adjacent contact of said first column toward a first direction of brush member movement such that said brush member switches off each contact of said second column prior to said adjacent contact of said first column when moving in a second direction opposite to said first direction. 
     
     
       5. A close-up photography control apparatus as defined in claim 4, wherein said one end of said second column contacts correspond respectively to said standard photography position, said first close-up position, said telephoto position, and said second close-up position, and said control means stops said lens barrel driving means when said brush member switches off an appropriate one of said second column contacts while moving in said second direction. 
     
     
       6. A close-up photography control apparatus as defined in claim 5, wherein said contacts for defining said first close-up zone and said second close-up zone are connected to a common output terminal, and said contacts for defining said standard photography zone and said telephoto zone are connected to individual output terminals, whereas all of said second column contacts are connected to another common output terminal. 
     
     
       7. A close-up photography control apparatus as defined in claim 1, wherein said close-up determination means includes automatic subject distance measuring means. 
     
     
       8. A close-up photography control apparatus as defined in claim 1, further comprising switch means for actuating said control means to change over said lens barrel between said standard photography position and said telephoto position. 
     
     
       9. A close-up photography control apparatus as defined in claim 1, further comprising a stepping motor for focusing, said stepping motor moving said taking lens system independently of said lens barrel driving means. 
     
     
       10. A close-up photography control apparatus as defined in claim 9, wherein said taking lens system comprises a front lens group and a rear lens group, and said stepping motor selectively moves one of said front and rear lens groups. 
     
     
       11. A method of controlling close-up photography for a variable focal length camera having a lens barrel movable in the direction of the optical axis of a taking lens system held therein thereby to change the focal length of said taking lens system, and an encoder comprising a brush member movable in proportion to said lens barrel along a contact pattern switched on and off by said brush member, said contact pattern including at least a column of contacts for defining a standard photography zone, a first close-up zone, a telephoto zone, and a second close-up zone covering respectively said standard photography position, said first close-up position, said telephoto position and said second close-up position; said method comprising the steps of: monitoring signal patterns output from said encoder;   detecting an existing position of said lens barrel based on said signal patterns;   setting said lens barrel in a predetermined standard photography position or in a predetermined telephoto position;   determining whether a subject to be photographed is disposed in a range nearer than a predetermined minimum focusable distance;   moving said lens barrel into a first close-up position when it is determined that said subject is in said nearer range and said lens barrel is in said standard photography position; and   moving said lens barrel into a second close-up position when it is determined that said subject is in said nearer range and said lens barrel is in said telephoto position.   
     
     
       12. A method as defined in claim 11, wherein said lens barrel is always stopped immediately after moving in one direction. 
     
     
       13. A method as defined in claim 12, wherein said lens barrel is always stopped upon said brush member passing beyond an end of an appropriate contact of said contact pattern in said one direction as to switch off said contact. 
     
     
       14. A method as defined in claim 12, wherein said lens barrel is moved into said standard photography position after an exposure is performed at said first close-up position. 
     
     
       15. A method as defined in claim 12, wherein said lens barrel is moved into said telephoto position after an exposure is performed at said second close-up position.